Atomic‐Scale Study on Core–Shell Cu Precipitation in Steels: Atom Probe Tomography and Ab Initio Calculations

In the present work, the atomic interactions among Cu, Al, and Ni elements in body‐centered cubic (BCC) ‐iron matrix, focusing on the formation mechanism of nano‐sized core–shell Cu precipitates, are investigated. In this study, using a combination of atom probe tomography, density‐functional theory (DFT) calculations, and molecular dynamics simulations, insights into the atomic‐scale migration tendencies of these elements in the supersaturated solid solution surrounding Cu precipitate in the martensite phase of a medium‐Mn steel are provided. In the results, it is shown that Ni and Al atoms are not expelled by Cu atoms but are instead attracted to the bcc‐iron matrix, forming a stable co‐segregation in the outer shell. This phase effectively surrounds the nano‐sized Cu precipitate and prevents its rapid growth, contributing to improved mechanical properties. In these findings, a theoretical method is offered for developing Cu‐contaminated circular steels by utilizing DFT calculations to unravel bonding preferences and assess the potential for forming a stable precipitation phase around nano‐sized Cu precipitates.